# NTSB ERA23LA013: Schempp-Hirth Discus CS, N520RJ, Woodstock, VA, October 8, 2022 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: October 8, 2022, 09:50 local (13:50 UTC) - Place: Woodstock, VA - Coordinates: 38.88205, -78.557789 - Nearby events: https://openairdocs.org/map.md?lat=38.8820&lon=-78.5578&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO, BFU - NTSB case key (mKey): 106089 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA23LA013 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/106089/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=106089 - Page: https://openairdocs.org/ntsb/ERA23LA013 ## Probable cause Improper repair of a crack by maintenance personnel, which resulted in a subsequent failure of the glider canopy. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance: repair](https://openairdocs.org/ntsb-findings/02062015): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Schempp-Hirth DISCUS CS, 1 case](https://openairdocs.org/ntsb-findings/02062015/cases.md?model=38019VS), [All aircraft, 99 cases](https://openairdocs.org/ntsb-findings/02062015/cases.md) - [Doors: passenger/crew doors](https://openairdocs.org/ntsb-findings/01035210): Aircraft › Aircraft structures · Failure (probable cause); cases with it: [Schempp-Hirth DISCUS CS, 1 case](https://openairdocs.org/ntsb-findings/01035210/cases.md?model=38019VS), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01035210/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [Schempp-Hirth DISCUS CS, 1 case](https://openairdocs.org/ntsb-events/338/sequence.md?model=38019VS), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) ## Analysis The pilot reported that the glider was at 3,700 ft mean sea level when the canopy suddenly, without warning, separated from the glider. He subsequently landed uneventfully at his intended destination airport. Review of maintenance records revealed that about 2 years before the accident, a maintenance facility stop-drilled a hole to correct a canopy crack at the rear hinge along the glide frame. Metallurgical examination revealed that the drilled hole appeared to halt progression of the original crack along its initial propagation direction. However, both the new primary separation crack and a secondary crack propagated from the hole in diametrically opposite directions, which suggests they likely developed due to a stress state along the same plane. Additionally, both cracks propagated from internal surface corners of the hole, indicating the corners likely acted as stress risers that facilitated crack initiation. There was no approved method from the glider manufacturer to stop-drill a hole in plexiglass; however, manufacturer approval was not required as the glider was registered in the experimental category. The glider manufacturer stated that it was common practice for cracks in the plexiglass to be drilled-out to stop the crack progression as a temporary solution; however, for a proper repair, the canopy must be removed and re-glued. The presence of multiple cracks propagating out of the same stress riser of the internal hole corner indicated that the specific hole drilled did not prevent subsequent progression of further cracking and the eventual separation of the canopy. ## Factual narrative On October 8, 2022, about 0950 eastern daylight time, an experimental Schempp-Hirth Discus CS glider, N520RJ, was substantially damaged when it was involved in an accident near Woodstock, Virginia. The private pilot was not injured. The glider was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the glider was at 3,700 ft mean sea level when the canopy suddenly, without warning, separated from the glider. The pilot double-checked the canopy latch and jettison handle and confirmed that he did not jettison the canopy. He subsequently landed uneventfully at his intended destination airport. Review of maintenance records revealed a work order dated August 9, 2020, which stated “…Found canopy crack at rear hinge along frame and stop holed crack….” Separated sections of the glider canopy were recovered and forwarded to the National Transportation Safety Board Materials Laboratory, Washington, D.C. Metallurgical examination revealed that the drilled hole appeared to halt progression of the original crack along its initial propagation direction. However, both the primary separation crack and a secondary crack propagated out of the hole in diametrically opposite directions, consistent with occurrence due to a stress state along the same plane. Additionally, both cracks propagated from internal surface corners of the hole, consistent with the corners acting as stress risers that facilitated crack initiation (for more information, see Materials Laboratory Factual Report in the public docket for this accident). According to a representative from the glider manufacturer, the canopy was made from plexiglass and there are no manufacturer instructions for repairing cracks in the canopy. Additionally, it has been common practice for decades that cracks in the plexiglass are drilled out to stop the crack progression as a temporary solution; however, for a proper repair, the canopy must be removed and re-glued. ## Aircraft - Registration: [N520RJ](https://openairdocs.org/aircraft/N520RJ), registered now, S/N 217CS, built 1996 (OpenAirDocs) - Reported make and model: SCHEMPP-HIRTH DISCUS CS (NO SERIES) - Registry model: [Schempp-Hirth DISCUS CS](https://openairdocs.org/model/schempp-hirth-discus-cs) (registry code 38019VS) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Glider - Serial number: 217CS - Year built: 1996 - Airframe hours: 839 - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Skyline Soaring Club Inc - Registered owner: Skyline Soaring Club Inc - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, July 27, 2022 - Departed: FRR, Front Royal, VA - Destination: Same as departure - Airport: VG55, Burner Airport, runway 03, 3,100 × 100 ft, grass/turf - Equipment: Electronic flight bag or handheld device, Electronic multifunction display, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 62; injuries: none; private; airplane ratings: single-engine land; last flight review May 7, 2022; seat: single; restraint: 4-point; flight hours: 317 total, 4 in this make and model, 202 as pilot in command, 6 in the last 90 days, 1 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 350° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 50 °F, dew point 41 °F - Altimeter: 30.29 inHg - Observed at: KFRR, 12 nm away - METAR: KFRR 081335Z AUTO 35004KT 10SM CLR 10/05 A3029 RMK AO1 ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20221008016539A](https://openairdocs.org/incident/20221008016539A), Oct 8, 2022: Schempp-Hirth DISCUS CS, Substantial damage. On October 8, 2022, at approximately 0945 local time, aircraft [privacy data omitted] a Schempp-Hirth glider was flying at approximately 3700 feet, when… ## Docket (7 files) The files NTSB released with the investigation on May 30, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=106089. 10.2 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16159231&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Pilot statement (item 2, PDF, 3 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16158649&FileExtension=pdf&FileName=Pilot%20Statement_Redacted-Rel.pdf - Memorandum for the record - glider manufacturer (item 3, PDF, 1 page, 144 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17085739&FileExtension=pdf&FileName=MFR-Rel.pdf - Excerpts from maintenance records (item 4, PDF, 2 pages, 5.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16158984&FileExtension=pdf&FileName=Mx%20Excerpts_Redacted-Rel.pdf - Photo array (item 5, PDF, 5 pages, 5 photos, 754 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16159303&FileExtension=pdf&FileName=Photo%20Array-Rel.pdf - Materials laboratory factual report (item 6, PDF, 12 pages, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16158773&FileExtension=pdf&FileName=Materials%20Laboratory%20Factual%20Report%2023-065-Rel.pdf - Evidence control form (item 7, PDF, 1 page, 55 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16158783&FileExtension=pdf&FileName=Evidence%20Control%20Form-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.